1. Field of the Invention
This invention relates generally to rolling mill oil film bearings, and is concerned in particular with an improved seal assembly for use in such bearings.
2. Description of the Prior Art
A typical rolling mill oil film bearing and its associated seal assembly is disclosed in FIG. 1. In this type of bearing, a tapered section 10 of the roll neck leads from a roll end face 12 to a continuing tapered section 14 having a sleeve 16 fixed thereto by any known means, e.g., one or more keys 18. The sleeve in turn is surrounded by a bushing 20 fixed within a chock 22, with the chock being spaced axially from the roll end face to define a circular gap 23 therebetween. A circular seal assembly 24 spans the gap and is internally subdivided by coacting seal components into inboard and outboard chambers 26,28.
During rolling, the roll is cooled by externally applied rolling solutions, and the roll neck is rotatably supported on a film of oil supplied continuously between the sleeve 16 and bushing 20. The externally applied rolling solutions are mainly deflected away from the bearing by the seal assembly 24. Any rolling solution which penetrates into the seal assembly is captured in the inboard chamber 26 and drained away to the mill sump through a lower outlet opening 27.
Oil escaping from between the sleeve 16 and bushing 20 is captured in the outboard chamber 28 and drained through a bore 30 in the chock to a sump 32. From here, the oil is returned through horizontal piping 34, T-connections 36 and flexible hoses 38 to vertical piping 40 leading to the mill lubrication system. The lubrication system cools and filters the oil before recirculating it to back the bearings.
The vertical piping 40 includes vents 42 for admitting air into the oil drainage system. During normal operating conditions, the level of oil outflow is as indicated schematically at 44. The outflowing oil continuously entrains and removes air from the outboard chamber 28, and that air is continuously replenished by an inflow of air (indicated by broken arrows) admitted via the vents 42. Thus, a balanced pressure is maintained between the inboard and outboard chambers 26, 28 which allows the seal assembly to function normally.
However, should air inflow become restricted or interrupted, either due to blockage of the vents, or filling of the drain lines with oil due to restricted drainage, then continued removal of entrained air from the outboard chamber will reduce the pressure in that chamber to below atmospheric. This in turn will cause the oil level to rise, eventually reaching a level at which the seal assembly is no longer able to perform adequately, resulting in oil leakage.
Conventional externally protruding or exposed venting devices have been considered but rejected because of the potential for damage and consequent leakage or blockage as a result of exposure to mill scrap, wrecks, improper handling, etc.
A primary objective of the present invention is to insure that the outboard chamber 28 is continuously supplied with air in sufficient quantity to replace the air being entrained with the outflow of oil, irrespective of the oil level in the bearing drainage system and/or the condition of the drainage vents.
A companion objective of the present invention is to achieve the aforesaid continuity of air supply by a venting arrangement which is completely contained within the seal assembly and thus immune from damage or blockage caused by exposure to a sometimes hostile mill environment and/or mishandling by mill personnel.